AC System ... new problem identified!

My '99 has 260k miles, and is getting a bit "long in tooth". I live in the hot SouthEast and need to have good ac. For the past few years, the front unit has been very unproductive for making cool air. The most effective way to get any cooling up front was to turn the rear unit to full blast ac and direct some of the cool air to the front ... this can make rear passengers somewhat uncomfortable ... and on very warm days was not very effective anyway. You could feel a bit of cooling come out of the front vents to believe something was working, just not very well. A lot of condensate drained out of the rear unit onto the ground, but the front unit ... just a few drops.

Hunting for the problem... Since the rear unit cooled pretty well, one could assume there is no issue with the ac compressor, the radiator fans, or the ac condensor, or amount of refrigerant.

There was plenty of air velocity coming out of the front vents, so therefore there is no issue with the front cabin fan, or cabin filter, or air vent system.

Next to be checked was the blend door and blend door actuator ... all found to be working perfectly!

That leaves the front evaporator coil itself. Could it just be dirty? The glove box, front fan and motor, heater coil and cover, blend door actuator ... were all removed. The blend door must be propped up ... or removed (my selection). Now, with mirrows and flashlight the coil can be peeked at. The coil was not very dirty but cleaned just the same. The problem ... was observed to be an ineffective coil surround insulator. The bottom of the coil was still mounted in a good foam cushion. But about 75% of the coil's perimeter had no insulation. Fan air was free to move around the coil and not pass thru it!
I think if the insulation had been placed properly by the installer, it would still be there ... but being "out of place", it had disintegrated over time and disappeared into the cabin interior.

The fix ... Some rope-shaped duct caulking ("Mortite") was picked up from Home Depot. Short pieces were pushed into place around the coil where needed.

Voila' ... frigid air again! It is colder than I remember it being before! It even sounds cold!

Very good informations 120unces thank you. Do we have enought room (according to the parts you have removed for access) to be able to install the caulking (Mortite) around the coil?

Yes, there is room ... better for skinny folks tho. Because of the shape of the plenum, it is more effective to place the caulking on the secondary side of the ac coil ... the same side as the heater coil and the blend door ... you will agree once you are "in there" and see the situation. In my case, some of the old insulation was still hanging loose, danging in the air stream and not achieving anything ... I just broke it away, cleaning up the ac coil periphery as much as possible before installing new caulking.

My blend door was removable because I had already cut an access way into the plenum and done the blend door fix a few years ago ... as outlined in other postings. But for this particular insulation repair, just propping the blend door "up" would work just as well.

The "Mortite" rope caulking is easy to work with; much like modeling clay. It must be forced deeply into place around the outside of coil if one expects it not to later come loose.

Thank you the additional informations, I will also take a look on my own system which is not as cold as before, and according to my A/C gauge my R134A level is OK so maybe it is the same problem as you have experienced.